Iwona Jasser

The influence of macrophytes on a phytoplankton community in experimental conditions

The impact of submerged macrophytes or their extracts on planktonic algae was studied under experimental conditions. Live Ceratophyllum demersum L., its extract, and extracts of four other plant species induced modifications in the phytoplankton dominance structure. These modifications were: a decline in the number of Oscillatoria limnetica Lemm., which was the most numerous cyanobacterian species, and a decline in biomass and percentage contribution of all cyanobacteria to total algal biomass. This was accompanied by an increase in biomass and percentage contribution of green algae, especially Chlorella sp. and Chlamydomonas sp. Also, there was an increase in biomass and percentage contribution of nanoplankton (under 50 µm) to total phytoplankton biomass.The isolation of planktonic algae from direct influence of C. demersum by means of dialysis membranes caused an increase in number, biomass and percentage contribution of cyanobacteria. Release of organic compounds of over 3000 daltons by macrophytes apparently contributed to a decline of cyanobacteria by changing the phytoplankton dominance structure.

A novel phylogenetic clade of picocyanobacteria from the Mazurian lakes (Poland) reflects the early ontogeny of glacial lakes

The community of picocyanobacteria inhabiting the Great Mazurian Lakes system (comprising lakes ranging from mesotrophic to hypertrophic) is dominated by phycoerythrin-rich cells, which outnumber phycocyanin-rich cells, even in hypertrophic lakes. The genetic diversity and phylogeny of 43 strains of picocyanobacteria isolated from four Mazurian lakes were studied by analyzing the nucleotide sequences of the 16S rRNA gene and cpcBA-IGS operon. Phylogenetic analyses assigned some of the strains to several previously described clusters (Groups A, B, C, E and I) and revealed the existence of a novel clade, Group M (Mazurian), which exhibited a low level of similarity to the other clusters. Both phycocyanin and phycoerythrin picocyanobacteria were assigned to this clade based on an analysis of the 16S rRNA gene. The cpcBA sequence analysis assigned only phycocyanin strains to Group M, whereas the phycoerythrin strains from the M ribogroup were assigned to Groups B and E. We hypothesize that Group M originally contained only phycocyanin picocyanobacteria. The phycoerythrin found in strains belonging to ribogroup M seems to have been acquired through horizontal gene transfer as an adaptation to the changing environment early in the ontogeny of these glacial lakes.

Molecular (PCR-DGGE) versus morphological approach: analysis of taxonomic composition of potentially toxic cyanobacteria in freshwater lakes.

BackgroundThe microscopic Utermöhl method is commonly used for the recognition of the presence and taxonomic composition of potentially toxic cyanobacteria and is especially useful for monitoring reservoirs used as drinking water, recreation and fishery resources. However, this method is time-consuming and does not allow potentially toxic and nontoxic cyanobacterial strains to be distinguished. We have developed a method based on denaturing gradient gel electrophoresis (DGGE) of the marker gene ITS and the mcy-gene cluster, and DNA sequencing. We have attempted to calibrate the DGGE-method with a microscopic procedure, using water samples taken in 2011 from four lakes of the Great Mazurian Lakes system.ResultsResults showed that the classic microscopic method was much more precise and allowed the classification of the majority of cyanobacterial taxa to the species or genus. Using the molecular approach, most of the sequences could only be assigned to a genus or family. The results of DGGE and microscopic analyses overlapped in the detection of the filamentous cyanobacteria. For coccoid cyanobacteria, we only found two taxa using the molecular method, which represented 17% of the total taxa identified using microscopic observations. The DGGE method allowed the identification of two genera of cyanobacteria (Planktothrix and Microcystis) in the studied samples, which have the potential ability to produce toxins from the microcystins group.ConclusionsThe results confirmed that the molecular approach is useful for the rapid detection and taxonomic distinction of potentially toxic cyanobacteria in lake-water samples, also in very diverse cyanobacterial communities. Such rapid detection is unattainable by other methods. However, with still limited nucleotide sequences deposited in the public databases, this method is currently not sufficient to evaluate the entire taxonomic composition of cyanobacteria in lakes.

Predicting blooms of toxic cyanobacteria in eutrophic lakes with diverse cyanobacterial communities

We investigated possibility of predicting whether blooms, if they occur, would be formed of microcystin-producing cyanobacteria. DGGE analysis of 16S-ITS and mcyA genes revealed that only Planktothrix and Microcystis possessed mcy-genes and Planktothrix was the main microcystin producer. qPCR analysis revealed that the proportion of cells with mcy-genes in Planktothrix populations was almost 100%. Microcystin concentration correlated with the number of potentially toxic and total Planktothrix cells and the proportion of Planktothrix within all cyanobacteria, but not with the proportion of cells with mcy-genes in total Planktothrix. The share of Microcystis cells with mcy-genes was low and variable in time. Neither the number of mcy-possessing cells, nor the proportion of these cells in total Microcystis, correlated with the concentration of microcystins. This suggests that it is possible to predict whether the bloom in the Masurian Lakes will be toxic based on Planktothrix occurrence. Two species of toxin producing Planktothrix, P. agardhii and P. rubescens, were identified by phylogenetic analysis of 16S-ITS. Based on morphological and ecological features, the toxic Planktothrix was identified as P. agardhii. However, the very high proportion of cells with mcy-genes suggests P. rubescens. Our study reveals the need of universal primers for mcyA genes from environment.

Distribution of invasive Cylindrospermopsis raciborskii in the East-Central Europe is driven by climatic and local environmental variables

Mechanisms behind expansion of an invasive cyanobacterium Cylindrospermopsis raciborskii have not been fully resolved, and different hypotheses, such as global warming, are suggested. In the East-Central Europe, it is widely occurring in western part of Poland but only in single locations in the East due to some limiting factors. Therefore, broad-scale phytoplankton survey including 117 randomly selected lakes in Poland and Lithuania was conducted. The results showed that C. raciborskii occurred widely in western part of Poland but was absent from other regions and Lithuania except one lake. The regions in which C. raciborskii was present had higher annual mean air temperature, higher maximum air temperature of the warmest month and higher minimum temperature of the coldest month, demonstrating that average air temperature, and indirectly, the duration of growing season might be more important factor driving C. raciborskii distribution than measured in situ water temperature. In turn, the presence of C. raciborskii in single localities may be more related to physiological adaptations of separated ecotype. Collectively, these results provide novel evidence on the influence of temperature on C. raciborskii distribution in East-European regions but also indicate high ecological plasticity of this species.

Fading out of the trophic cascade at the base of the microbial food web caused by changes in the grazing community in mesocosm experiments

Biomanipulation of consumer populations can have strong top-down impacts on the composition and biomass of lower trophic levels. In this paper, we assess how changes in crustaceans’ biomass influence classical grazing and the microbial food web in an oligo-mesohumic, low-pH lake (Mazurian Lake District, Poland). Removal of mesozooplankton from the experimental mesocosms created a gradient of crustacean biomass resulting in the biomass increase of rotifers, phytoplankton and protozooplankton, while autotrophic eukaryotic picoplankton (eu-APP) and bacteria were not affected. The strongest modifications concerned the rotifer biomass and phytoplankton community structure. Our results imply that the trophic cascade generated in the experiment did not extend to bacteria and eu-APP.

The relationship between autotrophic picoplankton (APP) - the smallest autotrophic component of food web and the trophic status and the depth of lakes

Abstract The occurrence and dynamics of autotrophic picoplankton (APP) in relation to the trophic status of a lake is discussed basing on results from 9 lakes situated in northeastern Poland and southern Finland. The lakes varied in the concentration of basic nutrients, chlorophyll a, phytoplankton biomass, pH depth and the composition of APP. A positive relationship between the productivity of the lakes and the APP biomass was confirmed. Shallow lakes were characterised by a significantly higher abundance and biomass of APP than deeper lakes, regardless of their trophic status. The abundance of APP as well as its contribution to the total phytoplankton biomass in the studied shallow lakes was also higher, than it could be expected from the level of basic nutrients in those lakes. Results imply that, when compared to deep lakes of a comparable trophic level, shallow and occasionally turbid water environment may create favourable conditions for APP, enabling it to occur in high numbers and thus influence the carbon cycling causing an increase of the carbon flow through the microbial food webs.

Life in Extreme Habitats: Diversity of Endolithic Microorganisms from Cold Desert Ecosystems of Eastern Pamir

ABSTRACT The aim of this study was to identify cyanobacteria diversity in rock communities from the cold desert ecosystem in Eastern Pamir Mountains (Tajikistan) and assess if the rock type and rock`s porosity can be indicators of microbial diversity in this extreme environment. Seven samples were collected in July 2015 from hillsides (ca 4000–4500 m a.s.l.) of the Eastern Pamir Mountains. Petrographic and scanning microscopy (SEM) allowed for the characterization of the rocks inhabited by endolithic communities as granite, gneiss and limestone with variable porosity. Based on next-generation sequencing (NGS) of amplicon of V3–V4 hypervariable region of 16S rRNA gene, we established that Actinobacteria, Proteobacteria and Cyanobacteria dominated the endolithic communities of microorganisms in the rocks studied, which distinguishes these communities from those described for other cold arid regions. Chroococcidiopsis and Leptolyngbya were dominant genera in the cyanobacterial communities according to culture-dependent analysis, as well as microscopic analyses of endoliths scraps from the rocks. Culture-independent metagenomic analyses revealed that Microcoleus, Acaryochloris, Chroococcidiopsis and Thermosynechococcus reads were the most abundant from all reads and dominated interchangeably in the samples. Endolithic communities of microorganisms in the rocks from the cold desert shrubland of Eastern Pamir Mts. appear to be diverse and different from communities described for other cold deserts.